Display module

ABSTRACT

A display module to prevent the leakage current generated between a first electrode layer and a second electrode layer that constitute a pixel via an organic light emitting layer and obtains uniform luminance. An interlayer insulation layer is provided between an edge of a first electrode layer and an organic light emitting layer that constitute the pixel and the distance between the edge and a second electrode layer is secured sufficiently. Further, the interlayer insulation layer ILI is coated with a resin material having fluidity, and flatness is improved as a whole. An aperture that accommodates the organic light emitting layer is formed in this interlayer insulation layer and the coated organic light emitting layer is formed in uniform thickness and through a necessary and sufficient spread.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.12/056,638, filed Mar. 27, 2008 now U.S. Pat. No. 8,232,934, which, inturn, is a Continuation of U.S. application Ser. No. 11/245,203, filedOct. 7, 2005 (now abandoned), which, in turn, is a Continuation of U.S.application Ser. No. 11/113,173, filed Apr. 25, 2005, and now U.S. Pat.No. 6,977,463, which, in turn, is a Continuation of U.S. applicationSer. No. 10/102,910, filed Mar. 22, 2002, now U.S. Pat. No. 6,888,304,and the entire disclosures of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to an active matrix type display module,and, more particularly, to a display module provided with a pixelcomposed of an emitting device, such as an electro luminescence elementor an LED (light emitting diode) that emits light by applying thecurrent to an emitting layer, such as an organic semiconductor thin filmand a pixel circuit that controls the light emission operation of thispixel.

BACKGROUND OF THE INVENTION

In recent years, with the advent of advanced information society, thedemand of a personal computer, a car navigation system, a portableterminal unit, a telecommunications system or these combined products isincreasing. A thin, lightweight, and low power consumption displaydevice is suitable for a display means of these products and a liquidcrystal display module or a display module that uses an electroopticelement, such as a self light emission type EL element or an LED isused.

The display module that uses the self light emission type electroopticelement of the latter is provided with features, such as goodvisibility, a wide viewing angle, and suitability for a motion imagedisplay with a fast response, and is assumed to be suitable for an imagedisplay in particular.

A display that uses an organic EL element (also called an organic lightemitting diode, and may also be hereinafter abbreviated to an OLED) ofwhich the emitting layer has organic matter in recent years is greatlyexpected as an OLED display in cooperation with a rapid improvement ofluminous efficiency and the progress of network technology that enablesvisual communication. The OLED display has the diode structure in whichan organic light emitting layer is sandwiched between two electrodes.

In order to increase the power efficiency in the OLED displayconstituted using such OLED, as described later, an active matrixdriving method in which a thin film transistor (hereinafter referred toas a TFT) is used as a switching element of a pixel is effective.

An art that drives an OLED display in the active matrix structure isdescribed in Japanese Patent Application Laid-open No. HEI04-328791,Japanese Patent Application Laid-open No. HEI08-241048, or the U.S. Pat.No. 5,550,066, for example, and an art related to a driving voltage isdisclosed in International Publication No. WO98/36407.

A typical pixel structure of the OLED display has a pixel drivingcircuit (also hereinafter referred to as a pixel circuit) including twoTFTs (the first TFT is a switching transistor and the second TFT is adriver transistor) that are first and second active elements and astorage capacitance (data signal holding element, that is, a capacitor),and this pixel circuit controls the emitting luminance of an OLED. Apixel is arranged in each intersection unit in which M data lines towhich a data line (or an image signal) is supplied and N scanning lines(also hereinafter referred to as gate lines) to which a scanning signalis supplied are arranged in a matrix of N rows multiplied by M columns.

For the drive of a pixel, a scanning signal (gate signal) issequentially supplied to N rows of gate lines and a switching transistoris set to the on state (turned on). Subsequently, the scanning in thevertical direction is finished once within a one-frame period Tf and aturn-on voltage is re-supplied to the first (first-row) gate line.

In this driving scheme, the time when the turn-on voltage is supplied toa gate line is less than Tf/N. Usually, about one sixtieth second isused as the value of the one-frame period Tf. While the turn-on voltageis being supplied to a certain gate line, all switching transistorsconnected to the data line are set to the on state, and a data voltage(image voltage) is supplied to M columns of data lines simultaneously orsequentially synchronizing with the on state. This is usually used by anactive matrix liquid-crystal display.

A data voltage is stored (held) in a storage capacitance (capacitor)while a turn-on voltage (hereinafter, turn-on is also merely referred toas ON. Equally, turn-off is also merely referred to as OFF) is suppliedto a gate line, and is kept in almost their value for a one-frame period(or one-field period). The voltage value of the storage capacitancespecifies the gate voltage of a driver transistor.

Accordingly, the value of the current that flows into the drivertransistor is controlled and light emission of an OLED is controlled.The response time until voltage is applied to the OLED and the lightemission starts is usually less than 1 □s, and even an image (motionimage) of a quick movement can be followed up.

Incidentally, in an active matrix driving method, because light emissionis performed over a one-frame period, high efficiency is realized. Thedifference is clear in comparison with a passive matrix driving methodin which diode electrodes of an OLED are directly coupled to a scanningline and a data line respectively and driven without providing any TFT.

In the passive matrix driving method, because the current flows into theOLED only while the scanning line is being selected. Accordingly, toobtain the same luminance as the light emission of a one-frame periodfrom only the light emission of the short period, the emitting luminancemultiplied by almost the number of lines is required in comparison withthe active matrix driving. To attain the purpose, the driving voltageand the driving current must inevitably be increased. However, a powerconsumption loss, such as generation of heat, is increased and the powerefficiency is decreased.

Thus, the active matrix driving method is assumed to be more superior tothe passive matrix driving method from the standpoint of a reduction inpower consumption.

SUMMARY OF THE INVENTION

In an active matrix driving method of an OLED, when the current issupplied to a capacitor for holding a display over a one-frame period,the one-handed electrode of the capacitor is connected to an outputterminal of a switching transistor and the other-handed electrode isconnected to a common potential line for the capacitor or a currentsupply line through which the current is supplied to the OLED.

FIG. 12 is a block diagram for typically describing one configurationexample of a conventional display module that uses an OLED, and FIG. 13is an explanatory drawing of the pixel configuration in FIG. 12. Thisdisplay module (image display module) is constituted by arranging a datadriving circuit DDR, a scanning driving circuit GDR, and a currentsupply circuit CSS around a display unit AR (inside enclosed by a dottedline in the drawing) formed on a substrate SUB composed of an insulatingmaterial, such as glass, in a matrix array of multiple data lines DLsand multiple gate lines, that is, scanning lines GLs.

The data driving circuit DDR has a complementary circuit consisting ofN-channel and P-channel type TFTs or a shift register circuit, a levelshifter circuit, and an analog switch circuit composed of a singlechannel type thin film transistor of only an N channel or a P channel.Besides, the current supply circuit CSS uses only a bus line, and canalso be constituted so that the current will be supplied from anexternal power supply.

FIG. 12 shows a system by which a common potential line COML for acapacitor is provided in the display unit AR, and the other-handedelectrode of the capacitor is connected to this common potential lineCOML. The common potential line COML is drawn out from a terminal COMTof a common potential supply bus line COMB to an external commonpotential source.

As shown in FIG. 13, a pixel PX has a first thin film transistor TFT 1that is a switching transistor arranged in the area enclosed by a dataline DL and a gate line GL, a second thin film transistor TFT2 that is adriver transistor, a capacitor CPR, and an organic light emitting diodeOLED. The gate of the thin film transistor TFT1 is connected to the gateline GL and the drain is connected to the data line DL. The gate of thethin film transistor TFT2 is connected to the source of the thin filmtransistor TFT1 and the one-handed electrode (positive electrode) isconnected to this connection point.

The drain of the thin film transistor TFT2 is connected to a currentsupply line CSL and the source is connected to an anode AD of theorganic light emitting diode OLED. The other-handed end (negativeelectrode) of the capacitor CPR is connected to the common supply lineCOML (FIG. 12). The data line DL is driven by the data driving circuitDDR and the scanning line (gate line) GL is driven by the scanningdriving circuit GDR. Further, the current supply line CSL is connectedto the current supply circuit CSS of FIG. 1 via a current supply busline (not shown).

In FIG. 13, when a pixel PX is selected by the scanning line GL and thethin film transistor TFT1 is turned on, an image signal supplied fromthe data line DL is stored in the CPR. Further, when the thin filmtransistor TFT1 is turned on, the thin film transistor TFt2 is turnedon, current from the current supply line CSL flows into the OLED, andthis current continues over almost a one-frame period (or a one-fieldperiod, and so forth). The current that flows on this occasion isspecified according to a signal charge stored in the capacitor CPR. Theoperation level of the capacitor CPR is specified according to thepotential of the common potential line COML. Accordingly, the lightemission of the pixel is controlled.

Because this system needs to provide the common potential line COML bypiercing through part of a pixel region, what is called an apertureratio is decreased and the improvement of brightness as a whole displaymodule will be suppressed. Further, the number of production processesfor providing the common potential line COML is increased.

FIG. 14 is the same block diagram for typically describing anotherconfiguration example of a conventional display module that uses anOLED. In this example, the basic placement of the thin film transistorsTFT1, TFT2 and the capacitor CPR that constitute each pixel is the samedisplacement as FIG. 13, but differs in that the other end of thecapacitor CPR is connected to the current supply line CSL.

That is, when a pixel PX is selected by the scanning line GL and thethin film transistor TFT1 is turned on, an image signal supplied fromthe data line DL is stored in the capacitor CPR. If the thin filmtransistor TFT2 is turned on when the thin film transistor TFT1 isturned off, the current from the current supply line CSL flows into theOLED. This current continues over almost a one-frame period in the samemanner as FIG. 13. The current that flows on this occasion is specifieda signal charge stored in the capacitor CPR. The operation level of thecapacitor CPR is specified according to the potential of the currentsupply line CSL. Accordingly, the light emission of a pixel iscontrolled.

In this type of the display module described in FIGS. 12 to 14, thesource electrode of the thin film transistor TFT2 that forms a firstelectrode layer (for example, anode) AD of the organic light emittingdiode OLED is formed using a conductive thin film, such as ITO (indiumtin oxide), and the first electrode layer AD of each pixel PX isisolated individually. Accordingly, an electric field is concentrated onan edge of the first electrode layer AD and the leakage current may begenerated between the edge and a second electrode layer (for example,cathode) CD.

FIG. 15 is a sectional view for describing the structure near a pixel ofa display module that uses an organic light emitting diode. This displaymodule is constituted by piling up a polycrystalline siliconsemiconductor layer PSI that uses low temperature polycrystallinesilicon as an ideal material, a first insulation layer IS1, a gate line(gate electrode) GL that is a scanning line, a second insulation layerIS2, a source electrode SD formed using an aluminum wire, a thirdinsulation layer IS3, a passivation film PSV, a first electrode layerAD, an organic light emitting layer OLE, and a second electrode layer CDon a glass substrate SUB.

When a thin film transistor (this thin film transistor is a drivertransistor) composed of the polycrystalline silicon semiconductor layerPSI, the gate line GL, and the source electrode SD is selected, anorganic light emitting diode formed using the first electrode layer ADconnected to the source electrode SD, the organic light emitting layerOLE, and the second electrode layer CD emits light and the light L isincident on the outside from the substrate SUB.

In the configuration part of this organic light emitting diode, the edgeof the first electrode layer AD or the edge of the second electrodelayer CD is close to the second electrode layer CD or the firstelectrode layer AD via the thin organic light emitting layer OLE. Insuch structure, the following problem is easy to occur.

FIG. 16 is an enlarged drawing of the part shown by the A of FIG. 15. Asshown in the same drawing, an electric field is concentrated on the edgeof the first electrode layer AD or the second electrode layer CD.Accordingly, the organic light emitting layer OLE is dielectricallybroken down between the second electrode layer CD and the firstelectrode layer AD and leakage current X is easy to occur. When suchleakage current X occurs, a high current flows from the current supplyline CSL into a thin film transistor and will damage the thin filmtransistor. When the thin film transistor is damaged, what is called apoint defect occurs and a display fault will be produced.

Further, because a scanning line, a data line or two thin filmtransistors, and a capacitor are formed on a substrate SUB in amulti-layered structure, even if the top of the second electrode layercoated with the organic light emitting layer is flat, the flatness ofthe periphery is extremely low. Therefore, dispersion occurs in thespace between the first electrode layer and the second electrode layer,and the same leakage current as above occurs in the part where bothelectrode layers are adjacent each other.

An organic light emitting layer is coated using a method, such asprinting coating, coating using ink jet, or spin coating. Because thecoating material of the organic light emitting layer used in suchcoating has fluidity, if the flatness of a coating surface and itsperiphery is low, the coated organic emitting material flows into theperiphery or is piled up in a part of the periphery. Accordingly, it isdifficult to form the organic light emitting layer in uniform thicknessand through a necessary and sufficient spread over the predeterminedpixel region.

When an organic light emitting layer differs in its thickness and spreadevery pixel, a difference occurs in each emitting luminance and thebrightness in all screen areas becomes uneven, thereby disablingacquisition of a high image quality display.

An object of the present invention is to provide a display module thatenables a high quality display by preventing the leakage currentgenerated between a first electrode layer and a second electrode layerthat constitute a pixel via an organic light emitting layer and formingthe organic light emitting layer that constitutes the pixel in uniformthickness and through a necessary and sufficient spread over thepredetermined pixel region.

To attain the above object, the present invention prevents thegeneration of leakage current between a first electrode layer and asecond electrode layer, as described above, by providing an interlayerinsulation layer between an edge of the first electrode layer and anorganic light emitting layer that constitute a pixel and sufficientlysecuring the distance between the edge and the second electrode layer.

Further, the present invention improves flatness as a whole by using aresin material with fluidity in the interlayer insulation layer, formingan organic light emitting layer accommodation unit on this interlayerinsulation layer, and forming the coated organic light emitting layer inuniform thickness and through a necessary and sufficient spread over thepredetermined pixel region.

By using this configuration, the leakage current that is generatedbetween a first electrode layer and a second electrode layer thatconstitute a pixel via an organic light emitting layer is prevented.Further, because the organic light emitting layer that constitutes thepixel is formed in uniform thickness and through a necessary andsufficient spread over the predetermined pixel region, a display modulethat enables a high quality display can be obtained. A more specificconfiguration example of the present invention is described below. Thatis,

(1) A display module is provided with multiple scanning lines arrangedin a matrix on a substrate, multiple data lines that intersect themultiple scanning lines, and a current supply line that supplies displaycurrent to a pixel and has a pixel every intersection unit of each ofthe scanning lines and each of the data lines, wherein

the pixel has an active element selected by the scanning line, a dataholding element that holds a data signal supplied from the data line bythe turn-on of this active element, and an emitting device that emitslight by the current supplied from the current supply line in accordancewith the data signal held by the data holding element,

the emitting device has a first electrode layer driven by the activeelement, an organic light emitting layer applied on the first electrodelayer, and a second electrode layer formed on the organic light emittinglayer, and

an interlayer insulation layer is provided between the first electrodelayer and the second electrode layer in the periphery of a lightemission unit formed in the lamination structure of the first electrodelayer, the organic light emitting layer, and the second electrode layer.

(2) In (1), the interlayer insulation layer provides an aperture inwhich the organic light emitting layer is accommodated in the coatingregion of the organic light emitting layer that constitutes the lightemission unit.

(3) In (2), the interlayer insulation layer is formed by being coatedwith a fluidity resin.

(4) In (3), an acrylic resin is used as the fluidity resin.

(5) In any one of (1) to (4), the display module has at least either aninsulation layer or a passivation film between at least a part of thefirst electrode layer and the substrate, and an aperture in which theorganic light emitting layer is accommodated in at least either theinsulation layer or the passivation film.

(6) In any one of (1) to (5), the interlayer insulation layer is formedby covering an edge of the first electrode layer.

(7) In (6), the interlayer insulation layer is formed by covering alledges of the first electrode layer.

By using the above configuration of (1) to (7), the distance between theedge of the first electrode layer and the edge of the second electrodelayer is secured sufficiently and the generation of leakage currentbetween the first electrode layer and the second electrode layer isprevented via an organic light emitting layer.

(8) A display module is provided with multiple scanning lines arrangedin a matrix on a substrate, multiple data lines that intersect themultiple scanning lines, and a current supply line that supplies displaycurrent to the pixel and has a pixel every intersection unit of each ofthe scanning lines and each of the data lines, wherein

the pixel has an active element selected by the scanning line, a dataholding element that holds a data signal supplied from the data line bythe turn-on of this active element, and an emitting device that emitslight by the current supplied from the current supply line in accordancewith the data signal held by the data holding element,

the emitting device has a first electrode layer driven by the activeelement, an organic light emitting layer applied on the first electrodelayer, and a second electrode layer formed on the organic light emittinglayer, and

an interlayer insulation layer formed by coating a fluidity resin isprovided between the first electrode layer and the second electrodelayer in the periphery of a light emission unit formed in the laminationstructure of the first electrode layer, the organic light emittinglayer, and the second electrode layer.

(9) In (8), an acrylic resin is used as the fluidity resin.

(10) In (8) or (9), the interlayer insulation layer is formed bycovering an edge of the first electrode layer.

(11) The interlayer insulation layer is formed by covering all edges ofthe first electrode layer.

(12) In any one of (8) to (11), the first electrode layer is formedusing ITO.

By using the above configuration of (8) to (12), because an organiclight emitting layer that constitutes a pixel is formed in uniformthickness and through a necessary and sufficient spread over thepredetermined pixel region in addition to the effect according to theabove configuration of (1) to (7), a display module that enables a highquality display can be obtained.

Besides, the present invention is not limited to the above configurationand the configuration of the embodiments described later, and, needlessto say, enables various modifications without deviating from a technicalidea of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described indetail based on the followings, wherein:

FIG. 1 is a typical sectional view near a pixel for describing theconfiguration of a first embodiment of a display module according to thepresent invention;

FIG. 2 is a typical drawing for describing a cross section near a pixelin the order of a production process in which an example of theproduction process of the display module of the first embodiment isdescribed in the display module according to the present invention;

FIG. 3 is a typical drawing in the vicinity of a pixel for describing alight emission mechanism of the display module according to the presentinvention;

FIG. 4 is a typical sectional view in the vicinity a pixel fordescribing the configuration of a second embodiment of the displaymodule according to the present invention;

FIG. 5 is a typical sectional view in the vicinity a pixel fordescribing the configuration of a third embodiment of the display moduleaccording to the present invention;

FIG. 6 is a typical sectional view in the vicinity a pixel fordescribing the configuration of a fourth embodiment of the displaymodule according to the present invention;

FIG. 7 is a top plan view near a pixel for describing an example of thecircuit configuration of the display module according to the presentinvention;

FIG. 8 is a typical sectional view in the vicinity a pixel fordescribing the configuration of a fifth embodiment of the display moduleaccording to the present invention;

FIG. 9 is a top plan view near a pixel for describing an example of thecircuit configuration of the display module according to the presentinvention shown in FIG. 8;

FIG. 10 is a top plan view for typically describing an example of thecircuit placement of the display module according to the presentinvention;

FIG. 11 is a top plan view for typically describing an example of theaperture position of a pixel provided corresponding to the circuitplacement of FIG. 10;

FIG. 12 is a block diagram for typically describing a configurationexample of a conventional display module using an organic emittingdevice;

FIG. 13 is an explanatory drawing of the pixel configuration in FIG. 12;

FIG. 14 is the same block diagram as FIG. 13 for typically describinganother configuration example of the conventional display module thatuses the organic emitting device;

FIG. 15 is a sectional view for describing the structure in the vicinityof a pixel of a display module that uses the organic emitting device;and FIG. 16 is an enlarged drawing of the part showing by A of FIG. 15.

DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention are described in detail below withreference to the drawings of the embodiments.

An organic light emitting layer provided in each pixel that is notshown, but is described later performs a monochromatic or color displayby emitting light in the luminance that is proportional to a currentvalue and a color (including white) that depends on the organicmaterials and performs the color display that emits by combining a colorfilter, such as red, green, or blue with an organic layer that emitswhite light.

FIG. 1 is a typical sectional view near a pixel for describing theconfiguration of a first example of a display module according to thepresent invention. The display module that uses an active matrix typeorganic light emitting diode (OLED) shown in FIG. 1 has a thin filmtransistor of each element formed on an insulating substrate SUB, suchas glass, using a polycrystalline silicon layer PSI.

The thin film transistor of this embodiment has a first insulation layerIS1, a gate line (scanning line) GL, a second insulation layer IS2, asource line SD, and a third insulation layer IS3 on the polycrystallinesilicon layer PSI, and an ITO pattern that becomes a first electrodelayer is formed on a passivation film PSV formed on the upper layer unitof the third insulation layer IS3. This first electrode layer AD isconnected to the source line SD through a contact hole perforated bypiercing into the passivation film PSV and the third layer 1S3.

Subsequently, before an organic light emitting layer OLE is coated onthe passivation film PSV, an interlayer insulation layer ILI withfluidity composed of an acrylic resin is coated and the smoothness ofthe surface is improved. At the same time, an aperture is formed in thepixel region of the interlayer insulation layer ILI by a processingmeans, such as a photolithographic technique. This aperture is formedonly in the area required for providing an organic light emitting layerinside the pattern of the first electrode layer AD.

Accordingly, a recessed part in which the interlayer insulation layerILI becomes an inside wall having a taper and a flat first electrodelayer AD is exposed at the bottom is formed in the pixel region. Bycoating this recessed part with an organic light emitting layer OLE, auniform organic light emitting layer OLE in necessary thickness isaccommodated and formed in the pixel region. Further, the organic lightemitting layer OLE coated around the pixel region is isolated from thefirst electrode layer AD in the interlayer insulation layer ILI.

After the organic light emitting layer is coated, the upper layer iscovered and a second electrode layer CD is formed. A metal film issuitable for this second electrode layer CD. Because the interlayerinsulation layer ILI has a taper, what is called step disconnection isdifficult to occur in the organic light emitting layer OLE and thesecond electrode layer CD applied on it. The second electrode layer CDformed at an edge around the organic light emitting layer OLE isisolated from the first electrode layer AD including the edge.Accordingly, the generation of leakage current between the edge ofeither the first electrode layer AD or the second electrode layer CD orbetween the edge of both electrode layers is prevented sufficiently.

Thus, according to this embodiment, the distance between an edge of afirst electrode layer and a second electrode layer that constitute apixel is secured sufficiently and the generation of leakage currentbetween the first electrode and the second electrode layer via anorganic light emitting layer is prevented. Further, because the organiclight emitting layer that constitutes the pixel is formed in uniformthickness and through a necessary and sufficient spread over thepredetermined pixel region, a display module that enables a high qualitydisplay is obtained.

FIG. 2 is a typical drawing for describing a cross section near a pixelin the order of a production process in which an example of theproduction process of the display module of the first embodiment isdescribed in the display module according to the present invention. Thisembodiment uses a thin film transistor of what is called the top gatestructure, but also uses a thin film transistor of what is called thebottom gate structure in the same manner. This process is describedbelow in the order of steps (1) to (11).

(1) A polycrystalline silicon semiconductor layer PSI is patterned on aglass substrate SUB and laser annealing for crystallization is applied.

(2) A first insulation layer IS1 is formed on it.

(3) A gate line (scanning line) GL is formed by depositing andpatterning a conductive thin film, such as titanium (Ti) or tungsten(W).

(4) A second insulation layer IS2 is formed and a contact hole isperforated at a necessary place.

(5) An aluminum wire that becomes a source electrode SD is formed (asthe need arises, the top and bottom of an aluminum thin film aresandwiched between materials of titanium (Ti) or tungsten (W).

(6) A third insulation layer IS3 is formed by covering an aluminum wire.

(7) Further, a passivation film PSV is formed using p-Sin. A contacthole that pierces into this passivation film PSV and the thirdinsulation layer IS3 and reaches the source electrode SD is perforated.

(8) A first electrode AD is formed by depositing ITO. This firstelectrode layer AD is connected to the source electrode SD via thecontact hole.

(9) An interlayer insulation layer ILI for insulating an organic lightemitting layer from an edge of the first electrode layer AD is formed.Further, an aperture is perforated in the pixel region required forlight emission and at a place necessary for external connection in theinterlayer insulation layer ILI. The interlayer insulation layer ILIuses an acrylic resin with fluidity. A taper is formed on an inside wallby applying heat when the aperture pattern of the pixel region isformed.

(10) The aperture of the pixel region is coated with an organic lightemitting layer OLE. The coating of the organic light emitting layer OLEis performed by a method, such as mask printing or ink jet.

(11) A metal layer is formed by covering an organic light emitting layerOLE and a second electrode layer CD.

After the above process, a display module is completed by being sealedin a sealing can or with a proper member, such as glass and ceramics,and being put into a module.

FIG. 3 is a typical drawing in the vicinity of a pixel for describing alight emission mechanism of the display module according to the presentinvention. The same reference symbol as FIG. 1 corresponds to the samepart. Further, the arrow mark using the reference symbol I of thedrawing shows a path of the current that yields to light emission.

A thin film transistor TFT is a driver transistor. When this thin filmtransistor TFT is selected by a gate line GL, the current I having acurrent value of a gray scale that matches a data signal held in acapacitor is supplied to a first electrode layer AD of an organic lightemitting diode OLED through the thin film transistor TFT (see FIG. 14).

In an organic light emitting diode OLED, an electron from a secondelectrode layer CD and a hole from a first electrode layer AD arerecombined in the organic light emitting layer OLE and light L of aspectrum that matches material characteristics of the organic lightemitting layer OLE is emitted. The first electrode layer AD isindependent every pixel and the second electrode layer is formed allover in a film shape concerning all pixels.

The current that passes through an organic emitting device OE from athin film transistor TFT flows out via a current drain line that is notshown from a second electrode layer CD. A two-dimensional display moduleis constituted by arranging such many pixels in a matrix.

FIG. 4 is a typical sectional view near a pixel for describing theconfiguration of the second example of the display module according tothe present invention. The same reference symbol as FIG. 1 correspondsto the same function part. In this embodiment, the film thickness of theinterlayer insulation layer ILI shown in FIG. 1 is about 1 μm, whereasthe volume of an aperture (recessed part) in which an organic lightemitting layer OLE is accommodated is increased by thickening the filmthickness 2 or 3 μm, for example.

This embodiment has the structure suitable when an organic lightemitting layer OLE is coated using an inkjet system. When the organiclight emitting layer OLE is coated using the inkjet system, an organicemitting material splashes from an inkjet nozzle into the aperture of aninterlayer insulation layer and reaches a first electrode layer AD withthe material diluted in some solvent and with the volume increased.

On this occasion, because the volume of an aperture is increased(deepened), a color mixture of both apertures of adjacent pixels can beprevented. Moreover, the color mixture into the adjacent pixels canfurther be prevented effectively by smoothing the tapered angle of aninside wall that forms the aperture of an interlayer insulation layer.

That is, according to this embodiment, an organic light emitting layerapplied to each pixel can be isolated clearly and deterioration in thesaturation of a luminous color can be prevented in addition to theeffect of the embodiment described above. Besides, mask printing andspin coating systems as well as an inkjet system can be applied to thecoating of the organic light emitting layer OLE.

FIG. 5 is a typical sectional view near a pixel for describing theconfiguration of a third example of the display module according to thepresent invention. The same reference symbol as FIG. 1 corresponds tothe same function part. This embodiment further increases the volume ofan aperture (recessed part) in which the insulation layer IS and thepassivation film PSV are removed from the pixel region and an organiclight emitting layer OLE is accommodated.

The interlayer insulation layer ILI is formed in the inside wall of therecessed part that is an aperture. The insulation layer of an organiclight emitting layer OLE is formed on a first electrode AD and opens atthe bottom of the recessed part. The organic light emitting layer OLE isaccommodated in this aperture and the second electrode layer CD isformed on it.

This embodiment is also suitable when an organic light emitting layerOEL is coated using an inkjet system and, in addition to the effect ofthe example, an organic light emitting layer applied to each pixel canbe isolated clearly and deterioration in the saturation of a luminouscolor can be prevented. Besides, mask printing and spin coating systemsas well as the inkjet system can be applied to the coating of theorganic light emitting layer OLE.

FIG. 6 is a typical sectional view near a pixel for describing theconfiguration of a fourth embodiment of the display module according tothe present invention. The same reference symbol as FIG. 1 correspondsto the same function part. In this embodiment, a second passivation filmPSV2 is further formed on a passivation film PSV (equals to a firstpassivation film PSV1) in the first embodiment described in FIG. 1.Another configuration is the same configuration as FIG. 1.

In this embodiment, in addition to the effect of the first embodiment,because the top layer is further flatten and the intrusion of anexternal gas and moisture is prevented more accurately, the reliabilityof a display module can be improved further. Besides, the secondpassivation film PSV2 can also be formed toward the second or thirdembodiments in the same manner.

FIG. 7 is a top plain view near a pixel for describing an example of thecircuit configuration of the display module according to the presentinvention. A pixel is formed in the area enclosed by a scanning line(gate line) GL and a data line DL. Besides, the reference symbol AD is afirst electrode layer (anode here) and CSL is a current supply line.

A pixel circuit has a first thin film transistor TFT1 (switchingtransistor), a second thin film transistor TFT2 (driver transistor), anda capacitor CPR. Further, an aperture DE that accommodates an organiclight emitting layer is provided in the part where the pixel circuit andeach wiring are prevented.

FIG. 8 is a typical sectional view for describing the configuration of afifth embodiment of the circuit configuration of the display moduleaccording to the present invention. The same reference symbol as FIG. 1corresponds to the same function part. This embodiment has theconfiguration in which the exit direction of light emission is set atthe opposite side with a substrate. In the drawing, CD′ indicates afirst electrode layer (cathode here) formed using a metal thin film andAD′ indicates a second electrode (anode here) formed using a transparentconductive film, such as ITO.

In this embodiment, the emission light in an organic light emittinglayer OLE exits from the second electrode layer AD′. Accordingly, asealing member that is not shown, but is provided on the side of thesecond electrode layer AD′ uses a transparent member, such as glass.

FIG. 9 is a top plan drawing near a pixel for describing an example ofthe circuit configuration of the display module according to the presentinvention shown in FIG. 8. The same reference symbol as FIG. 7corresponds to the same function part. A pixel is formed in the areaenclosed by a scanning line (gate line) GL and a data line DL in thesame manner as the above embodiment.

In this embodiment, an aperture DE that accommodates an organic lightemitting layer OLE needs not to be provided in the part where the pixelcircuit and each wiring are prevented. Accordingly, because theconfiguration of this embodiment is obtained, there is an advantage thata pixel having a high aperture ratio and a wide area can be formed. Onthe whole, a display module having a bright screen, and a display modulehaving low consumption power and a long life span can be obtained.

FIG. 10 is a top plan drawing for typically describing an example of thecircuit placement of the display module according to the presentinvention, and FIG. 11 is a top plan view for typically describing anexample of the aperture position of a pixel provided corresponding tothe circuit placement of FIG. 10. Each pixel is formed in the partenclosed by a scanning line GL driven in a scanning driving circuit GDRand a data line DL driven in a data driving circuit DDR and arranged ina matrix shape. A current supply line CSL branches at the outside of adisplay region AR from a current supply bus line CSB and arranged inparallel to the data line DL for each pixel.

Besides, PAD is a pad for externally supplying a signal and power to adisplay module via a flexible printed board. PAD1 indicates a pad for adata driver, PAD2 indicates a pad for a scanning driver, and PAD3indicates a current supply pad. Even each part of these pads forms anaperture in an insulation layer and a passivation film.

The aperture for applying an organic light emitting layer thatconstitutes the light emission area of a pixel is arranged in a matrixshape corresponding to each pixel as shown in FIG. 11. Further, thereliability of a display module is improved by also providing anaperture unit in a sealing unit that turns around a display region AR asthe need arises and improving the adhesion between a substrate and thesealing unit. Besides, an aperture that is a contact hole for connectinga second electrode layer to the bottom wiring layer is also formed.

Besides, the present invention is not limited to a display module thatuses the OLED described above, and can also be applied to anotherdisplay module that performs a display in the same light emissionoperation as the OLED.

As described above, according to the present invention, because theleakage current generated between a first electrode layer and a secondelectrode layer that constitute a pixel via an organic light emittinglayer is prevented and the organic light emitting layer that constitutesthe pixel is formed in uniform thickness and through a necessary andsufficient spread over the predetermined pixel region, a display modulethat enables a high quality display can be provided.

What is claimed is:
 1. An organic display module including a current supply line; a thin film transistor connected to the current supply line; a first electrode connected to the thin film transistor; an interlayer insulation layer provided on the first electrode, and having an aperture to expose at least a portion of the first electrode; an organic light emitting layer provided on the first electrode through the aperture; a second electrode covering the organic light emitting layer; and a passivation film covering the second electrode, wherein a surface of the passivation film has a higher degree of flatness than the second electrode, wherein the interlayer insulation layer includes a portion forming an inner wall of the aperture, said portion of the interlayer insulation layer having a taper to decrease in thickness in a direction from a top portion of the aperture toward a bottom portion of the aperture, the inner wall of the aperture being located between the organic light emitting layer and the first electrode layer; wherein, to form the surface with the higher degree of flatness of the passivation film compared with the degree of flatness of the second electrode, a thickness of the passivation film which is formed over the organic light emitting layer in the aperture is formed to be thicker than a thickness of the passivation film which is formed over the interlayer insulation layer.
 2. An organic display module according to claim 1, wherein the first electrode comprises an anode electrode, and the second electrode comprises a cathode electrode.
 3. An organic display module according to claim 1, wherein the first electrode comprises a transparent conductive layer and the passivation film is transparent.
 4. An organic display module according to claim 1, wherein an insulation layer is provided under the first electrode, and the first electrode is connected to the thin film transistor through a contact hole in the insulation layer.
 5. An organic display module according to claim 1, wherein the first electrode is comprised of a metal thin film, and the second electrode is comprised of a transparent conductive film. 